This non-provisional application claims priority under 35 U.S.C. xc2xa7 119 to Korean Patent Application No. 2002-45896 filed Aug. 2, 2002, the contents of which are incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to a method of manufacturing a semiconductor device, and more particularly, to a method of forming a pattern of a semiconductor device capable of reducing a proximity effect, a photomask that has a layout structure capable of reducing the proximity effect, and a method of exposing an object by using the photomask that has a layout structure capable of reducing the proximity effect.
2. Description of the Related Art
It is well-known that various patterns in semiconductor devices are formed by photolithography processes. In a photolithography process, a photoresist layer, whose solubility varies according to radiation (e.g., X-ray or ultraviolet light), is coated on a semiconductor wafer or coated on a layer (e.g., an insulating layer, a conductive layer, etc.) where patterns are to be formed. Next, portions of the photoresist layer are exposed to light, which alters the solubility of the exposed portions of the photoresist layer. The portions of the photoresist layer having a high solubility to a developing solution are then removed to form photoresist patterns. Using the photoresist patterns, exposed portions of the underlying layer to be patterned may be etched or otherwise processed to form various patterns such as wirings or electrodes.
As the integration of semiconductor devices increases, many new techniques are being explored to permit the formation of fine patterns. Examples of these new techniques include a method using an excimer laser where a short wavelength of light is used, an exposure method using a phase shift mask (PSM), and a modified illumination method, such as off-axis illumination.
The phase shift mask is a mask that uses interference or partial interference of light to expose a pattern having a desired size. Since light passing through the phase shifter has the reverse phase with respect to light passing through the other portion of the phase shift mask, the diffraction of light is utilized in reverse to increase a contrast of the pattern image.
Off-axis illumination is a method where vertical components of incident light are blocked by a lens aperture or a pupil and only oblique incident components of light illuminate a photomask. This method enhances resolution and depth of focus (DOF). However, when a first region where patterns are closely spaced (e.g., a dense region) and a second region where the patterns are not closely spaced (e.g., a sparse region) exist in the same layer, the pattern pitch (i.e., a value adding a linewidth of the pattern to a space between the patterns) of the first region becomes different from that of the second region. A proximity effect is caused due to an optical diffraction of the adjacent patterns in a place where the pattern pitch varies, which generates a pattern lifting or a bridge between the adjacent line patterns.
FIG. 1 is a plan view of a prior art photomask for forming first patterns and second patterns on a semiconductor device. A first region is depicted where the first patterns have a small size and are closely spaced (densely disposed) and a second region where the second patterns have a large size are not closely spaced (sparsely disposed) exist in the same layer on a semiconductor wafer.
Referring to FIG. 1, the conventional photomask includes first mask patterns 2 corresponding to the first patterns and second mask patterns 4 corresponding to the second patterns. The first mask patterns 2 have a first width (w1) and are spaced apart by a first space (s1). The second mask patterns 4 have a second width (w2) that is larger than the first width (w1) and are spaced apart by a second space (s2) that is wider than the first space (s1). The second mask pattern 4 and the first mask pattern 2 are separated by the first space (s1).
Due to the pitch difference of the first and second regions, the second mask pattern 4 adjacent to the first mask pattern 2 is subject to the proximity effect which generates a lifting of the second pattern transferred to the wafer or a bridge between the adjacent first and second patterns. For example, the lower portion of the second pattern is exposed due to the spread of light on the second space (s2) between the adjacent second mask patterns 4. Accordingly, an undercut is generated in the second pattern which causes a lifting of the second pattern.
Furthermore, with respect to the first space (s1) between the first mask pattern 2 and the second mask pattern 4, the exposure amount is decreased by an interference of the second mask pattern 4 having a wide width (w2), thereby enlarging the end linewidth of the first pattern adjacent to the second pattern. As a result, a bridge between the adjacent first and second patterns is generated.
To overcome the aforementioned problems, a method has been suggested which forms a scattering bar around the mask patterns on the photomask to correct the proximity effect. Although this method is effective for isolated patterns, it is not very effective for patterns that have different sizes and pitch variation. Because the scattering bar can only be inserted for the patterns having a wide space of 350 nm or more, the scattering bar is not effective for the patterns having a narrow space less than 350 nm.
At least one exemplary embodiment of the present invention provides a method of forming patterns of a semiconductor device that are capable of reducing the proximity effect.
At least one exemplary embodiment of the present invention provides a photomask that has a layout structure capable of reducing the proximity effect.
At least one embodiment of the present invention provides a method of exposing an object by using a photomask that has a layout structure capable of reducing the proximity effect.
At least one embodiment of the present inventionprovides a method of forming patterns of a semiconductor device having a first region where a plurality of first patterns are separated from each other by a first space and a second region including a plurality of second patterns that have a size that is larger than the size of the first patterns. The second patterns are separated from each other by a second space that is wider than the first space. The first and second regions are formed on the same layer. A fine gap that transmits light is formed in a central portion of a mask pattern corresponding to the second pattern on a photomask for patterning the first and second patterns to reduce the proximity effect.
In at least one exemplary embodiment of the present invention, the fine gap is formed to be less than half the size of the first pattern. The first pattern and the second pattern are spaced apart from each other by the first space. The second pattern is formed to be more than about twice the size of the first pattern.
At least one exemplary embodiment of the present invention provides a method of forming patterns of a semiconductor device having first line/space patterns of a first pitch and second line/space patterns of a second pitch that are larger than the first pitch. The first and second linespace patterns are formed from the same layer. A fine gap that transmits light is formed in a central portion of a mask pattern corresponding to the second line/space pattern on a photomask for patterning the first and second line/space patterns to reduce the proximity effect.
At least one other embodiment of the present invention provides a photomask for simultaneously forming a plurality of first patterns and a plurality of second patterns on an object by an optical method. The first patterns are separated from each other by a first space and the second patterns are separated from each other by a second space that is wider than the first space. The photomask includes a plurality of first mask patterns repeatedly disposed by the first space to correspond to the plurality of first patterns, a plurality of second mask patterns repeatedly disposed by the second space to correspond to the plurality of second patterns, and a fine gap that transmits light formed in a central portion of each of the second mask patterns.
Another exemplary embodiment of the present invention provides a method of exposing an object that includes placing a photomask over the object to form a plurality of first patterns separated by a first space and a plurality of second patterns having a size larger than that of the first pattern and being separated by a second space that is wider than the first space; and exposing the object by using the photomask. The photomask includes a plurality of first mask patterns separated from each other by the first space to correspond to the plurality of first patterns, a plurality of second mask patterns separated from each other by the second space to correspond to the plurality of second patterns, and a fine gap that transmits light formed in a central portion of each of the second mask patterns.
In at least one exemplary embodiment of the present invention, when a first region where first patterns having a small size are closely spaced (e.g., densely disposed) and a second region where second patterns having a large size are not closely spaced (e.g., sparsely disposed) exist in the same layer, a fine gap is formed in a central portion of a mask pattern of a photomask corresponding to the second pattern. As a result, the proximity effect is reduced to a pattern where the variation of pattern pitch occurs, thereby improving a lifting margin and a bridge margin to the adjacent patterns having a narrow space.